Due to a decreasing size of an image sensor and an increasing number of pads, the space between the pads gets smaller. Accordingly, higher requirements are set for packaging the image sensor.
Conventionally, the image sensor is generally packaged through a Wire Bonding. With the rapid development of integrated circuits, a size of a product cannot meet expectations due to long wires. Therefore, a Wafer Level Packaging (WLP) gradually takes the place of the Wire Bonding and becomes a common packaging method. In a WLP technology, an entire wafer is packaged, tested, and then cut into individual finished chips. The size of a packaged chip is same as that of a bare chip, which confirms to market requirements for lighter, smaller, shorter, thinner and cheaper microelectronic products.
In the case that image sensors are packaged with a conventional WLP technology, it is usually required to form a packaging cover at photosensitive regions of the image sensors to protect the photosensitive regions from being damaged and contaminated in a packaging process. The transmission of light may be affected even with a transparent packaging cover. The light may not be smoothly received and emitted at the photosensitive regions of the image sensors, thereby affecting overall performances of the chips. Hence, the packaging cover needs to be separated from the wafer at the end of the packaging process.